Method of making cementitious pipe



Patented Get. 24, 1933 1,932,150 I I METHOD or Maxine. CEMENTITIOUSPIPEManabu Tada, Tokyo, Japan, assignor to Frank W. Plane, Chicago, Ill.

No Drawing. Application JanuaryS, 1932 Serial No. 585,640 I 4 Claims.(01. 25-454) This invention relates to improvements in method of makingcementitious pipe.

In the making of cement pipe according to ordinary and well knownprocesses, it is custom- 5 ary to mold or form the pipe upon a core ormandrel while the cement is in a plastic condition, and thereafter toallow the cement to dry and harden upon the core until the cement hasbecome thoroughly set throughout, after which the core is removed fromthe interior and the pipe section allowed to become thoroughly cured andhardened before use. This method of making pipe is open to the objectionthat it requires a complete hardening of the pipe throughout before thecore is removed, which necessarily ties up the use of the cores for aconsiderable period of time, and at the same time involves difiiculty inthe removal of the cores from the thoroughly hardened pipe sections.

In the making of pipe by the common process, it is notfeasible to removethe core at an early stage in the drying and hardening operation andwhile the'cement or other cementitious material is in a plasticcondition, since an attempt to rei move the core at this stage wouldusually result in a deformation of the pipe either during or after theremoval of the core.

The present invention is designed to overcom the difficulties noted bysubjecting the pipe sec tions, while on the forms or cores, to a dryingor surface hardening in an atmosphere of carbon dioxide (00 which hasthe effect, by chemical reaction, of rapidly hardening the surface ofthe pipe to a degree suilicient to prevent deformation and to allow thecore to be thereafter removed while the interior surrounding the core isin a more or less plastic condition, so that the removal of the corewill be facilitated, thereby making the core available for further usewhile the pipe 9 sections are gradually drying out and setting, andobviating the necessity for completely hard ening the pipe sectionsbefore the cores are again available for use.

The present invention is particularly directed to the manufacture ofasbestos cement pipes,

wherein a pipe composed of a mixture of a..- bestos fibres and asuitable cementitious binder is formed upon the core and dried in adrying chamber supplied with heated gas containing CO2 until the outerportions only of the pipe are dried and stiffened, the inner portionsremaining moist and flexible, after which the core is removed and thedrying continued under normal atmospheric conditions. Although thenature of the chemical surface reaction which occurs when the plasticcementive composition is subjected to CO: is not thoroughly understood,it has beenfound that when cement is mixed with water and reacts with 00,1 obtain COBCa (calcium carbonate), which furnishes a very hard andquickly formed outer shell or hardened surfacefor the pipe section,which permits the form or core to be removed from the still plasticinterior of the pipe section without tending to disrupt or deform thesection either during the removal of the core or thereafter. Bythus-preliminarily case hardening the pipe sections in an atmospher'eof002, the sections can be sufficiently hardened, in a very short space oftime, to permit removal from the drying charn- 70, ber, after which thecores can themselves be removed and again used while the previouslyformed pipe sections are stacked up and allowed to thoroughly dry andharden throughout a sufficient period of time to condition them for use.i

In making pipe in conformity with the present method, it is notnecessary to use any special form of drying chamber or conveyor for thepipe sections, since the case hardening operation may be performed inany closed room or receptacle into which the pipe sections may beintroduced continuously or in batches, and subjected to the hardeningoperation for a sufficient period of time to secure an initial hardeningsufficient in v degree to permit the removal of the pipe sections fromthe cores without deformation. The particular length of time requiredwill depend to some extent upon the character of the cementitiousmixture employed and the diameter and thickness of the pipe sections andthe facilities available for the removal of the cores, but in all casesit is sufiicient only to allow them to remain in the CO2 atmosphere fora suflicient period of time to secure the necessary hardening requiredto facilitate the subsequent manipulation of the pipe sections andpermit them to be stacked or stored for final hardening.

Pipe sections manufactured in accordance with the present method, whencomposed of asbestos fibres and cement, will possess a close, firmtexture and relatively great strength, and at the same time they willreadily withstand the deleterious effects of gases or chemicals whichfrequently attack pipe manufactured wholly of cee 1,05 ment in theordinary way.

The pipe manufactured in accordance with the present invention ispeculiarly suitable for use in fiues or conduits for the passage ofsmoke or gaseaand in fact is useful under all conditions in whichsimilar piping is customarily employed, as well as under certainconditions which have heretofore precluded the use of ordinary cementpipe.

Although the method of the present invention has been described asapplicable to the manufacture of pipe sections, it is not the intention,unless otherwise indicated in the claims, to limit the invention to themaking of pipes, since other products formed of cementitious materialmolded to shape while in the plastic state may be advantageouslyhardened in the manner described and irrespective of the particularconfiguration of the products so treated.

I claim:

1. The method of hardening a cementitious product, which consists insubjecting the same while in a plastic state to an atmosphere containingCO2 in order to effect a quick surface hardening of the same sufiicientto render the product self-sustaining, and in thereafter removing saidproduct from said atmosphere while the interior portion remains soft andallowing the same to completely harden under normal atmosphericconditions.

2. The method of hardening a cementitious product, which consists in theforming of such a product on a core while in the plastic state andsubjecting said product upon the core to an atmosphere containing CO2 inorder to effect a surface hardening thereof sufficient to render theproduct self-sustaining prior to the removal of said product from thecore, and in thereafter removing said product from the core while theinterior surfaces contiguous to the core are still in a soft enoughcondition to permit easy removal of the core.

3. The method of hardening a cementitious product, which consists in theforming of such a product on a core while in the plastic state andsubjecting said product upon the core to an atmosphere containing CO2 inorder to effect a surface hardening thereof suflicient to render theproduct self-sustaining priorto the removal of said product from thecore, and in thereafter removing said product while mounted upon thecore from the atmosphere containing CO2, removing the product from thecore while the interior surface contiguous to the core is still in arelatively softoondition, and continuing the drying and hardening of theproduct under normal atmospheric conditions.

4. The method of hardening a cementitious pipe section, which consistsin forming said pipe section while in a plastic state upon a core, andsubjecting the pipe section while in a soft condition to an atmospherecontaining CO2 to effect asurface hardening of the pipe sectionsufficient to render the product self-sustaining, and in removing thepipe section from said atmosphere and thereafter removing the core fromthe pipe section While the interior surface of said section contiguousto the core is still in a soft condition, and in continuing thehardening under normal atmospheric conditions.

MANABU TADA.

